Process for reclaiming tar and light oil



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PROCESS FOB RECLAIMING TAB AND LIGHT OIL.

Application led December 17, 1924. Serial No. 756,881.

My invention relates to a method of and means for reclaiming tar andlight oils from the wash tar and wash oils which are produced as aby-product of the manufacture of water gas. y l

While I have applied my invention in practice to the recovery orreclaiming of tarA and oils from the otherwise refuse materials producedin the manufacture of water gas,

I do not intend to limit the invention to this particular use, as Ibelieve that the same apparatus and treatment will be applicable tomaterials of similar character from other sources and I consider thesame to come within scope of my invention.

ln the manufacture of water gas, the gas, after it is formed in thegenerator, passes over into the carbureter where petroleum oils arecracked to enrich the product. After passing the carbureter, the gaspasses through a superheater and then through a water seal and thenthrough a coolin or spray tower and from there to Yal1 equa izerreservoir. It may betreated for the removal of sulphur, and so forth, atintermediate stages, but the above stages are the essential steps in theprocess as now employed. 'The Water seal is relatively hot.

bubbles in the hydraulic main. Here a certain part of the tar and oilsare condensed out of the gas stream. Thel gas then passes on to thecooler and condenser, where it is further cooled and the tar and oilscondensed out of the same. The wash oils and tar pass the hydraulic mainan'd the condensate from the cooler or condenser are then run olf to asettling well where, according to the prior practice, the light oils arevented olf to atmosphere and the tar is supposed to settle orprecipitate. ,The

water or water solution of various salts is run back to the hydraulicmain.

It has been found that while some of the tar separates out readily, itis extremely difficult to cause the tar to settle or precipitatewherever it has formed an emulsion with the water. As a result, a gooddeal of the mixture or emulsion must be disposed of un'der difficulties,as it is not salable and it is only a nuisance.

' It appears that the mixture of tar, oils, and water' forms an emulsionwhich will not stratify or separate, and the material becomes impossibleto dispose of, as 1t often as passing through thej It is cooled bycontact with the water, through which it4 takes a longer time than canbe granted in the settling well for suilicient of the oil to evaporateor stratify and the tar to settle out, to make the liquid workable for awater.-

seal.

The stuff will not burn readily because of the large water content. Itcannot be sold as tar because of the large water content. It cannot bedisposed of for the oil that there is in it because no previously knownprocess of recovery has yielded suicient oils to make the process ofrecovery profitable. The liquid' emulsion cannot be discharged into thesewer as it clogs up the same. It cannot be discharged into a stream-orlake because of the deleterious effect on animal and vegetable life.Besides legislation has stopped this disposal. The tar, if it could begotten out, could be marketed, so long as it does not contain too greata percent of water. l

From my experience, I have found that the stuff is a serious problem. Itseems that the light oils which are combined with the tar make a mixtureor emulsion in water which emulsion has a specific gravity of` about1.01 to 1.03.V The slight -difference in specific gravity and therelative viscosity of the'mass prevents any separation of theconstituents by settling at ordinary temperatures and pressures.

the tar has a specific gravity of approximately 1.07 to 1.12. Thus, inan emulsion of say from 4 to 5% light oil, and tar around 10 to 15%, andwater between 70 to 90%, the resultant emulsion is of a specific gravityso near that of water, particularly when the water contains otherimpurities and salts, that ordinary gravity separation is not feasibleor effective.

A great many methods of separation have been tried. None is generallyapplicable to commercial operation. It costs more to separate theconstituents than they are worth. The most common method is to boil themixture to drive 0E the water, leaving the tar relatively free lofwater. This requires a great expenditure of heat to va orize 0E thewater. The tar may be raise' to approximately 400 to 500 F., and` eventhen the water is not all driven olf.

Another process that has been tried is that of centrifuging theemulsion. It has been generally unsuccessful, rst because of excessiveof the operation and, next be- The light oils have a y specific gravityof about 1.70 to .85, whereasY cause everything about the apparatus be'-comes clogged with heavy' tar and carbon.

Another method that has heretofore been tried is'working, churning, ormechanically f lthe other ingredients, or for extracting' any oremulsion.v

of theother ingredients from the mixture I have tried the matter ofboiling olf the Water and light oils, but I find that this is only anemergency process to get rid of the stuff. The immense, amount of heatrequired for vaporizingjo (latent heat of vaporization), say 70 to 85%of Water toget from 10'to 15% tar, makes the fuel cost higher than the.valueof the recovered material. The settling well is purposely leftopen to atmosphere, so that some of the light oils may `escape andassist in the precipitation of the'tar. This removes such light oils asa possible .by-productl as heretofore practiced.

Findlng that I wascompelled, by necessity, to disposejof. thel emulsion,I experimented with the material in a small experi-mental still with aglass side, .to permit of observation of .the action involved.

Upon heating up the. emulsion 'I found that .boiling of. the mass keptthe whole emulsion in such a state of agitation that,

the tar would only slowly settle out and it was necessary to drive ofthe water and light oils by continued boiling. The lastv part of thewater was found to be diilicult to extract. In fact, after thetemperature of the mass was run up above 400 F.,water vapor continued tocome'oi".

After a series vof experiments, I evolved the theory that the tar andlight oils are in close alliance 'or bond and that being so in bondtheir combined specific gravity is so near that of water, that thetarand oils' remain 1n suspension and vdo not precipitate or settle out.

I then conceived the idea that if it were possibleA to break the bond'between the oils and the tar, it-mightbe possible to secure a lowerviscosity andto secure a di'ere'ntiation in specific gravity, whichwould permit ltheoils to' goV to the top. l.and the tar to Sgo to thebottom. and Athusparting from the water.

VIn accorda1i`ce withfthis. theory, I slowly raised the temperature ofthe mixture by the iise of.exhaust.ste z u n and- I` found'that notrapid enough to cause agitation of the mass, but was conducted gently,so that the vlight oil vapors come olf slowly. As soon as this evolutionof oil vapors began, I noticed the precipitation of tar began. I gentlyand slowly raised the temperature vfurther and found that the evolutionof vapors suddenly stopped and, at a slightly higher temperature,evolution of further vapors began. I am not able to account for the'sudden and sharp-.cessation of vapor pressure which occurred, but Iassume. that it was due to the definite boiling points of the lighteroils, such as benzol, toluol, naphthol, xylol, etc.

I found that with the expenditure of very little heat, I was able todrive ofliv the light oils and precipitate la large part of the tar. Theemulsion was never brought to the boiling point of the water content.The light oils 'were easily condensed and formed a valuable by-product.

I have since conducted tests of the'process on a'commercial scale andfind that it works satisfactorily, rec ring light oils and tar withtheuse of e aust steam at about 3 to 5 lbs. gauge pressure. I have,therefore,- run the emulsion of wash oils and tar and water into aclosed well to conservethe light oils and I find that the yield of lightoils is thereby considerably increased.

While the process, .as at vpresent carried out, is a batch process,"Ibelieve, from my knowledge of the operationthereof, that itv msv caneasily be made a continuous process. I -I have, by my discovery,disposed ofan ex- -pen'sive nuisance about a gas plant "and turned thesameinto a profit. Now, in order to acquaint those skilled in the artwith the mannerv of constructing and operating a device embodying myinvention, I shall describe in connection with the accompanyingdrawings, a .speciic manner of carrying out the method.-

In the drawings:

Figure 1 is a diagram of a system in 'which my invention is embodied;-and Fig. 2 is a diagram illustrating my theory of the union of the tarand the light oils.

In Fig. 1 I have shown diagrammatically the operative parts of a watergas plant. The steam boiler 1 has a steam supply main 2, which isconnected through a valve 3 with the generator 4. The generator 4 is aclosed chamber in which a bed of fuel 5 is maintained upon suitablegrates, or the like. This fuel isadapted to be brought to incandescenceby means of a draft of air through the air supply pipe 6, the valve 7Hbustion pass through the discharge pipe 8 over to the carbureter9, thevalve in said pipe then being opened, and the valve 11 in pipe 12 beingclosed, so that the hot gases from the incandescent fuel bed 5 aredriven over through the carbureter, down through the brick checker work13 in said carbureter, through the pipe 14, and from thence through thesuperheater and out at the stack 16, valve. 17 at this time being openand valve 18 in the discharge pipe 19 vbeing closed.

The superheater 15 is-substantially lled with checker work 2O forabsorbing the heat Yoi the gases, which are then discharged toatmosphere. The carbureter has an oil supply pipe21, including a controlvalve 22, to permit gas oil to be discharged into the carbureter. Thisoil is supplied at approximately 125 lbs. pressure during the gasforming stage, as will be described later. `When the body of fuel 5 hasbeen brought to incandescence, the air valve 7 is closed, the valve 10of the discharge pipe 8 is closed, and valve 11 opened, and the stack 16is cuto valve 17 being closed, and the valve 18 in gas pipe 19, is thenopened, and steam from the boiler 1, through the main 2f and valve 3 isforced down through the fuel bed 5, discharge pipe 12, through thecarbureter 9, superheater 15, and over into the hydraulic main 23, wherethe pipe19 dips under thelevel of the liquid 24 to form a water seal.From thence the gas passes up through the pipe 25 into'the scrubber orcooling tower 26, where the ,gas is brought to substantially atmospherictemperature by means of a spray of water from the supply pipe 27.Instead of a spray vcondenser or cooling tower 26 a water tube condensermay be employed. The gas rises through the scrubber 26 or through thecondenser and thence'through pipe 28 it is discharged preferably bymeans of a suitable pump, into the equalizer tank 29, which is asuitable gas holder for equalizing the pressure and theY supply to thegas holder between periods'of operation of the generator. rlhe equalizer29 comprises an inverted cup having a water Seal, `as is well understoodby those skilled in the art, and this equalizer has a discharge pipe 30which leads to a gas holder and purifier of a kind well known in theart.

The structure thus far described is old yand operates in a Well knownmanner. The A generator and carbureter, together with superheater,operate on three minute intervals in normal operation, that is, threeminutes are devoted to bringing the generator to heat, and heating upthecarbureter and superheater, and then for three minutes the air isshut oil?, valves are reversed, steam is forced down through thegenerator and water gas is formed and oil is, at the same time, sprayed.into the carbureter to enrich the gas which is thus generated.

vtained in said separator.

The gas which is driven off from the generator 4 contains a certainamount of tar and oils in volatile form and the cracking of the gas oil,which is sprayed into the carbureter 9, results in the formation ofcertain oils and tar, which are carried in more or less vaporized form,over into the hydraulic main 23 and when the gas bubbles up through thewater seal 24, the tar and light oils are cooled and condensed andpicked up with the liquid in said water seal. At the saine time, thewater in the water seal absorbs a certain amount of ammonia, sulphurcompounds, and the like. rlhe cooling of the gas is completed in thecooling tower 26 or other suitable condenser. The liquid from thehydraulic main 24 and the condenser is discharged, as by way of the pipe31, to the receiving tank or well 32 which, according to my invention,is formed as a closed tank in order to avoid loss of the aromatic andother light oils which are carried by the water of the water seal overinto suoli receiving tank. This is a departure from the prior practicewhich was to vent the settling wellto atmosphere. rlhe condensate fromthe condenser 26 likewise is discharged through pipe 33 into thereceiving tank 32, so that said receiving tank receives the tar, lightoils, and liquid discharged from the hydraulic main and from thecondenser. This liquid contains the tar and light oils both in separateform and in the form of a water emulsion and, as explained heretofore,such, emulsion is extremely diiiicult to break up into its constituents.A certain part of the tar deposits in the bottom of the receiving tankand may be drawn oi at the pipe 35, sothat separation of such part isnot necessary. However, the part which will not separate by gravity ispumped out by means of a ump 36 and discharged into the separator 3 asby means of the pipe 38, wherex the liquid emulsion is subyected toheating by means of the steam coils 42 conrIhese heating coils 42 areconnected preferably to the engine 40, or live steam. may be admittedfrom the pipe 41 under the control of suitable valves. 'Ihe steam coils42 are adapted to discharge water drainage at 43, this water beingpreferably returned to the steam. boiler 1. The emulsion is subjected toheating by waste steam at approximately 3 to 5 lbs. pressure, thetemperatures of steam being approximately 230 F. However, theleinuL sionis not heated to the boiling point of water, but is kept at atemperature slight ly lower than the boiling point of water lby suitablycontrolling the supply of steam exhaust steam pipe 39 of the' condensercomprising, in this case, Ia coil of pipe cooled by a water jacket 46.A'ny other suitable form of condenser may be employed. In the winterseason no condensing water will be necessary. The light oils arecondensed in the coil and discharged into the receiving tank 47. `Theheating of the emul' sion is carried on for from 14 to 24 hours, thetime being a function of the steam temperature over the area'of theheating surfaces, to insure the thorough separation lof light oils andtar, and at thel end of this time 'the mixture is brought fairly closeto the boiling point of water, and all of the light oils which can beextracted at that temperature are driven olf. I contemplate circulatingthe mass in order to assist in the irst separation, but in the processas heretofore carriedV out, lI have not done so. At the en d of theheating process the water liquor will have completely separated from thetar.

All of the liquid which is separated by the water seal and thecondenser, and which may be termed tar and light oils and water which 1sdischarged into the tank 32, comprises approximately 30 t0' 50%commercial-tar and to 70%' of the emulsionlto which I '-have heretoforereferred. The water from maintaining a water seal at 23 because 4ittends to froth in the hydraulic main and may be drawn back into the gas`take off heating below the boiling point'of the `water,` but above theboiling point of the light Ch l does ebullition occur.'

pipe 19 and lthere catch7 ire. The emulsion..

is,'theref ore, pumped to the separator. and

is subjected to the treatment whichJI haveV above outlined. From `mystudy of the prob-f lem, I am of theopinion that the gradual oils, tendsto free the bond between the tar and the oils without appreciableagitation of the mixture. Apparently the freeing occurs in the massofthe liquid and the oiltends at once'to float to the top and the tar tosink to thebottom. Whether the oil rises otherwise disposed of. VIt canbe seen that my process is not the usual fractioning processfor takingofi' successive cuts from a still because first, I start with'anemulsion, not a solution and, second I dol not bring the mixture oremulsion to theA boiling point nor Finally the separation of water andtar is actual gravity separation aadnot fractionation. It appears to benecessary to vaporize 'off the oils'to get 'them out'of contact with thetar, otherwise` they would tend to re-combine.

I' have pictured in Fig. 2 diagramma-tically, what according-to mytheory is the'situation in the emulsion, namely, that a particle of tarand a particle of oil cling together,

the oil particle tending to raise the mass to' the top because the oilis'ofl a specific gravity of approximately .70 Ito .80, whereas the tartends to drop to the bottom, the tar being of a specific gravity ofapproximately 1.07 to 1.10. rlhe water or liquor in which [this emulsionisformed is somewhat' heavier will the tar precipitate. I conceive thatbyl bringing the entire mass to a temperature which is approximatelythat of the boiling point of the light oils, the oil and tar areseparated in the body of Water with the result that the tar precipitatesand ,the oil rises to the top and is there vaporized or recondensed atthe water level.

I conceive that this process-"can beI hastened by reducing theatmospheric pressure upon the mass to the point of lowering the boilingpointof the oil and thus causing separation. to try, but I believe itwill assist.. .Also, it may be hastened by increasing the heatingsurfaces or steam temperaturesof the heating coil.

Now while I have described a specific apparatus audits mode of operationto carry out my invention, I do not intend to be limited to the detailswhich I have shown and described, except as the same appear in theappended claims.

I claimf 1. The process of` precipitating tar and recovering light oilsfrom the emulsion coning the emulsion slowly to the boiling point of thelight oils but below the boiling oint of .the water admixedy therewithunti the' tar precipitates. l

2. The process of precipitating tar from:v

an emulsion of light oil, tar and water which comprises heating up' theemulsion to a temf perature below the boiling pointV of the This I havenotv yet beenv able.

ldensate of a gas plant which comprises heatwater admixed therewith, butat approxi# mately the boiling point of the light oil.

3. The process of separating-'light oils and 'tar from an emulsion ofwater which com` the mass to fa' temperature rises heatin elow the boilng point of water, but to-a tem erature high enough to evolve vapors.of t e llght oils, precipitating the4 tar 'at'the bottm' pf the mass 0fliquid, and separately @Qndnsmg the vapors of light Oils,... V

f1. The process of recovering light oils from a 'water emulsion of tarland oils washed out of the gases in a gas plant which consists inheating the emulsion to volatilize the light oils therein and free thetar by gravity, and withdrawing and condensing the volatilized oils.

5. The process of precipitating tar from an emulsion of water, tar andlight oils, whichV comprises warming the emulsion to free Suliicient ofthe oil from the tar to precipitate the tar by gravity.

6. The process of recovering tar from a (water emulsion of tar and oilswashed out of the gases in a gas plant 'which consists in warming theemulsion to free the. tar and the light oils Jfrom each other andseparating the tar by Settling of the water. s

7. The process of separating light oils and the lsame out of tar from anemulsion of water, which consists inheating the mass of liquid lluid toa temperature slightly above the boiling point of the light, oils, butbelow the boiling point of water, drawing off the resultant vapors oflight oils, causing the tar separated from the said light oils togravitate to the bottom of the mass of liquid fluid, condensing thelight oil vapors, and withdrawing the said tar from the bottom of theremaining mass of liquid.

8. The process of breaking up a water emulsion of tar and oils Washedout of the gases in a gas plant which consists in maintainingV the masscomparatively quiet-.-.and

' heating to a temperature above 170o F. and

below 212o F. at atmospheric pressure.

In witness whereof, I hereunto subscribe my name this 15th day ofDecember, 1924. WILLIAM F. DIETZSCH.

